WA warehouse fire not suspicious

A factory blaze that prompted a health warning to nearby residents in Perth's north has been deemed non-suspicious by police, while two other separate fires have been deemed arson.

Emergency Services were called to a fire at the pool supply warehouse in Balcatta, where various chemicals are stored, just before 8pm (WST) on Saturday.

Nearby residents were warned about the threat of potentially hazardous smoke and fumes in the air, but by 1.30am (WST) on Sunday, the blaze was under control and the health threat had passed.

Arson squad detectives investigated the incident on Sunday and said the blaze was not suspicious.

But a separate fire on Saturday night at a home in Neerabup, in Perth's north, where the offenders forced their way into a complex and set fire to property inside one of the units is being further investigated.

Police are also examining a suspicious fire reported about 4.15am (WST) on Sunday at a business in Northam, northeast of Perth.

Anyone with information about either incident is asked to call Crime Stoppers on 1800 333 000.